Texas Parks & Wildlife: Caddo Lake water cleaner than...

1of18PHOTOS: Salvinia at Caddo Lake
These photos show just how dramatically salvinia affects Caddo Lake. The photo on the left was taken in January 2018 after a freeze. The salvinia browned and eventually sunk into the water, leaving what is shown in the photo on the right a few months later.
>>> See more photos showing how the plant affects the lake Photo: Texas Parks and Wildlife

2of18Texas Parks & Wildlife officials also credit giant salvinia weevils, which feeds on the plant, with some of low salvinia levels.Photo: Texas Parks and Wildlife

3of18Giant salvinia is considered an invasive plant species that has been affecting the Texas side of Caddo Lake since 2006. Recently, the lake has recorded its lowest presence of salvinia in years.Photo: Larry D. Hodge, Texas Parks and Wildlife

5of18The fern also makes its way into boating equipment.Photo: Texas Parks and Wildlife

6of18PHOTOS: Threat to inland water
Giant salvinia is considered an invasive plant species that has been affecting the Texas side of Caddo Lake since 2006. Recently, the lake has recorded its lowest presence of salvinia in years.
>>> See more facts about salvinia Photo: Texas Parks and Wildlife

8of18A poster at a Texas Parks and Wildlife Department exhibit at the recent Toyota Texas Bass Classic on Lake Conroe offers a blunt assessment of the potential impact the invasive plant giant salvinia can have on fisheries.Photo: Shannon Tompkins, Chronicle

9of18Giant salvinia, a floating fern from South America, grows like a malignant cancer. It can double its mass in just a few days, quickly blanketing the water's surface and smothering any containing life. And it has no natural regulating forces in this country.

11of18Denied sunlight by the covering mat of salvinia, submerged and emergent vegetation — the “good” plants that provide food to waterfowl and other animals, cover for young fish and other creatures and pump oxygen into the water — whither and die.Photo: JIM KENNETT, BLOOMBERG NEWS

13of18A salvinia-covered waterbody is worthless for fish and fishing. But the plant negatively impacts a whole ecosystem as well, destroying its ability to support waterfowl.Photo: Kevin Fujii, Chronicle

14of18Without plants and oxygen, the fish and every other creature in the water die — suffocated. The result is a lifeless piece of water.Photo: Kevin Fujii, Chronicle

15of18Even if salvinia doesn't completely smother the large reservoirs it invades, it damages parts of them — coves and inlets get smothered. Those patches serve as cauldrons from which the plant spreads.Photo: Kevin Fujii, Chronicle

16of18When Texas begins seriously enforcing the laws prohibiting invasive species on boat trailers and hitting a few people with $500-per-plant fines, the word will get out that the problem is serious.Photo: JIM KENNETT, BLOOMBERG NEWS

17of18Invasive aquatic plants such as salvinia don't just impact a few bass fishermen. They can destroy entire ecosystems, ruining habitat for waterfowl and wading birds, otters and mink, crawfish and reptiles and any other life that depends on a healthy waterway.Photo: JIM KENNETT, BLOOMBERG NEWS

18of18Giant salvinia is just one of a depressingly expanding list of aquatic invasive species doing very real damage to Texas freshwater ecosystems. There's hydrilla, water hyacinth, alligatorweed, water lettuce, grass carp and more.Photo: JIM KENNETT, BLOOMBERG NEWS

Boaters, anglers and even wildlife recently have been living well at Caddo Lake, where the water has been at its cleanest in years thanks to an unusually low presence of giant salvinia, an invasive water fern that reduces flow and oxygen levels in the water.

Salvinia has been a notable presence on the Texas side of Caddo since 2006, hurting the water quality and affecting boat mobility, said Texas Parks & Wildlife District Fisheries Biologist Tim Bister. Since then, he said the plant has covered up to 6,000 acres of the total 12,000 acres around the only natural lake in Texas.

But the salvinia, which dies in cold weather and thrives in warm, took a major hit from last year's winter. And ongoing herbicide treatment in the area has kept salvinia's current coverage to around 1,300 acres, he said.

"We sprayed about 7,000 acres worth of salvinia from March up until the end of the year," Bister said. "We really did a good job to stay on top of it and keep the area from getting out of control."

Bister gave most of the credit for the decrease in salvinia to the cold weather and subsequent high water in 2017. That combination almost completely washed away the entire salvinia population before some grew back, he said.

In addition to the herbicide treatment, he said giant salvinia weevils, which feed on the plant, were able to re-establish their presence at the lake.

"The benefit of the weevil is you can put them in backwaters... where they start doing some control of their own," he said.

With a beautiful weather in the forecast for the upcoming weekend, he encouraged fishermen to come out and enjoy the waters. He also said people should still be mindful of other invasive plants.

"Fishing has always been good. So come and fish Caddo, but be aware that there's still some salvinia or other invasive species like hydrilla...that could be on a boat ramp," Bister said. "So make sure folks clean drain and dry their boat trailer and equipment before they go to a different lake."